Percy discovers a child's letter to Santa Claus forgotten at the bottom of his mail van on Christmas Eve, but he is determined to make things right, even if that means tracking down Mr. Claus himself! With help from Thomas and his friends, Percy travels through dazzling parades, sweet-smelling gingerbread bakes, and snowflake flurries on a quest to deliver the letter to Santa and make a child’s Christmas Wish come true.